Electrode catheters are known as medical devices used for diagnosing or treating irregular heartbeats of heart.
As an electrode catheter for measuring potential in a portion such as a pulmonary vein of heart, the present applicant has proposed an electrode catheter having a catheter shaft, an operating handle connected to a base end side of the catheter shaft, a catheter tip part formed in a circular loop shape connected to a tip side of the catheter shaft, plural ring-shaped electrodes attached to an outer periphery of the catheter tip part, and a tip electrode attached to a tip of the catheter tip side (see Patent Document 1).
The catheter shaft (catheter main body) constituting the electrode catheter described in Patent Document 1 has a single lumen structure (thin long tubular structure having one internal hole) having a resin tube (first tube) with relatively high rigidity and a soft resin tube (second tube) with relatively low rigidity.
Here, a preferred outside diameter of the catheter shaft is 2.3 to 2.4 mm (see [0021] to [0025] of Patent Document 1).
Thus, for example, when plural (for example, two to three) electrode catheters are passed through one sheath and inserted into a heart so as to measure intracardiac potentials simultaneously in plural regions, the outside diameter of the catheter shaft constituting these catheters is desirably smaller than an outside diameter which is preferred in Patent Document 1 (for example, 1.4 mm or less).
On the other hand, the electrode catheter needs to be changed in direction to select a blood vessel which reaches the target region, or needs to bend the tip portion of the catheter shaft largely when the electrode is pressed against the target position. Thus, the catheter shaft constituting the electrode catheter is required to have good kink resistance and torque transmissibility. Further, the catheter shaft needs to have a good pushability.
However, the catheter shaft having a small outside diameter as described above does not have good kink resistance and torque transmissibility because it has low rigidity. Further, the catheter shaft having a small outside diameter has a poor pushability.
Moreover, in a catheter shaft having the single lumen structure like the one constituting the electrode catheter described in Patent Document 1, lead wires extending inside the shaft and a pull wire for pulling operation which moves in an axial direction inside the shaft easily interfere with each other. Consequently, the lead wires may be damaged or broken. Further, the interference between the lead wires and the pull wire occurs more easily in a catheter shaft with a smaller outside diameter.